Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$150.79	8.824%	$164.0957	$164.10	$164.10	$164.10
Purchase #2	$155.30	4.377%	$162.0975	$162.10	$162.10	$162.10
Purchase #3	$85.56	4.200%	$89.1535	$89.15	$89.15	$89.20
Purchase #4	$154.51	7.539%	$166.1585	$166.16	$166.15	$166.20
Purchase #5	$222.65	11.418%	$248.0722	$248.07	$248.05	$248.10
Purchase #6	$142.42	3.619%	$147.5742	$147.57	$147.55	$147.60
Purchase #7	$47.30	8.424%	$51.2846	$51.28	$51.30	$51.30
7 purchase totals =	$958.53		$1,028.4362	$1,028.43	$1,028.40	$1,028.60